Power unit arrangement structure for motorcycle

ABSTRACT

In a motorcycle power unit, a crank shaft ( 56 ) and a clutch shaft ( 57 ) disposed on the right side (in the figure) from a body center ( 127 ) and a cylinder head ( 129 H) is disposed on the left side from the body center ( 127 ). Since the crank shaft, the clutch shaft and a transmission shaft are disposed on one of right and left sides with respect to the body center and the cylinder is disposed on the other side with respect to the body center, it becomes possible to make a favorable lateral balance of the power unit.

TECHNICAL FIELD

The present invention relates to a power unit arrangement structure fora motorcycle, and particularly to a power unit arrangement structuresuitable for a hybrid type motorcycle including an electric motor inaddition to an engine.

BACKGROUND ART

Vehicles of a type using gasoline engine as a drive source are mainlyavailable; however, vehicles of a type using an electric motor as adrive source are required at locations where occurrence of exhaust gasmust be avoided. A motor-driven vehicle, however, has an inconveniencein the increased body weight and the shortened running distance. To copewith such an inconvenience, it has been increasingly required to developa hybrid type vehicle including an electric motor in addition to anengine.

For example, Japanese Patent Laid-open No. HEI-8-175477 discloses ahybrid type motorcycle entitled “DEVICE FOR SWITCHING ENGINE POWERTO/FROM MOTOR POWER IN MOTORCYCLE OR THE LIKE”.

As shown in FIG. 2 of the above document, although a piston and acylinder are disposed along the center of a rear wheel 37 in the widthdirection of the vehicular body, main parts such as a transmission case12 and a belt type transmission are disposed on the left side (as seenfrom a passenger) with respect to the center of the rear wheel 37, andfurther a motor 22 shown in FIG. 3 of the above document is disposed ata position largely shifted leftward from the center of the rear wheel.

That is to say, in the related art power unit, it is expected to take alateral weight balance thereof.

DISCLOSURE OF THE INVENTION

It is therefore an object of the present invention to provide a powerunit arrangement structure capable of solving a lateral imbalance of apower unit.

To achieve the above object, according to the present invention, thereis provided a power unit arrangement structure for a motorcycle, inwhich a power transmission system for transmitting power of an engine isdisposable on one side of a rear wheel of the motorcycle, an engine isdisposed with a crank shaft extending in a longitudinal direction, thecrank shaft and the power transmission system are disposable on one sidewith respect to a longitudinal center of a motorcycle body, and acylinder head of the engine extends on the other side with respect tothe longitudinal body center, characterized in that a power transmissionshaft is disposed parallel to and higher than the crank shaft.

Since the crank shaft and the power transmission system are disposed onone side and the cylinder head is disposed on the other side, it ispossible to improve the weight balance of the power unit, and hence toensure a favorable steering stability of the motorcycle.

According to a further aspect of the invention, the cylinder head is acylinder head of a four cycle engine.

Since the crank shaft and the power transmission system are disposed onone side and the cylinder head including a valve drive mechanism isdisposed on the other side, it is possible to improve the weight balanceof the power unit, and hence to ensure a favorable steering stability ofthe motorcycle.

According to a still further aspect of the invention, the powertransmission system includes a power transmission system fortransmitting a power of an electric motor.

Since the power transmission system including the electric motor and thecrank shaft are disposed on one side and the cylinder head is disposedon the other side, it is possible to improve the weight balance of thepower unit, and hence to ensure a favorable steering stability of themotorcycle.

According to a still further aspect of the invention, members of anintake system and members of an exhaust system are disposed on thecylinder head side.

Since the crank shaft and the power transmission system are disposed onone side, and the cylinder head and members of the intake and exhaustsystem are disposed on the other side, it is possible to improve theweight balance of the power unit, and hence to ensure a favorablesteering stability of the motorcycle.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the present invention will be described indetail below, by way of example only, with reference to the accompanyingdrawings, in which:

FIG. 1 is a side view of a motorcycle according to the presentinvention;

FIG. 2 is a sectional side view of a power unit according to the presentinvention;

FIG. 3 is a sectional plan view of the power unit according to thepresent invention;

FIG. 4 is a view showing a configuration and a function of a cone typecontinuously variable transmission according to the present invention;

FIG. 5 is a view showing a configuration and a function of the cone typecontinuously variable transmission according to the present invention;

FIG. 6 is a view illustrating an engine lubricating system according tothe present invention;

FIG. 7 is a view illustrating a transmission lubricating systemaccording to the present invention; and

FIG. 8 is a front view of the power unit, showing a cam shaft drivemechanism as a valve drive mechanism according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be describedwith reference to the accompanying drawings. It is to be noted that thedrawings should be seen in the direction of reference numerals.

FIG. 1 is a side view of a motorcycle according to the presentinvention.

Referring to FIG. 1, a motorcycle 1 has at its lower central portion abox-like main frame 2 serving as a battery containing box. InverseU-shaped front swing arms 4 extend from a lower front portion of themain frame 2 through a front pivot 3, and a front wheel 5 is rotatablymounted on the front swing arms 4. A head pipe post 7 extends obliquelyupward from an upper front portion of the main frame 2 and a head pipe 8is fixed at a leading end of the head pipe post 7. A handle post 9 isrotatably mounted in the head pipe 8, and a steering arm 11 is mountedon a lower end of the handle post 9. A leading end (lower end) of thesteering arm 11 is connected to a knuckle 12 mounted on the front wheel5. A power unit 15 is swingably mounted on an upper rear portion of themain frame 2 through a rear pivot 13 functioning as a swing shaft. Arear wheel 16 is mounted on the power unit 15. A rear cushion 17 isdisposed in front of the rear wheel 16, and an air cleaner 18, anexhaust pipe 19, a muffler 21, and a tail lamp 22 are disposed behindthe rear wheel 16. A vehicular body includes a front fender 25, a frontcover 26, a front handle cover 27, a center cowl 28, a rear cowl 29 anda rear fender 31 which are disposed in this order from the front side tothe rear side of the vehicular body.

In FIG. 1, reference numeral 30 indicates a stem; 32 is a front brakedisk; 33 is a caliper; 34 is a resin spring; 35 is a front damper; 36 isa leg shield; 37 is a passenger's step; 38 is a side stand; and 39 is amain stand. On an upper side of FIG. 1, reference numeral 41 indicates ahorn; 42 is a front lamp; 43 is a handlebar; 44 is a grip; 45 is abaffle duct; 46 is a radiator; 47 is a fan; 48 is a sheet; 49 is ahelmet box; 51 is a helmet; 52 is a tail lamp; and 55 is a power unitcase.

The power unit case 55 is composed of right and left crank cases 55 band 55 a (the right crank case 55 b on the back side of the figure isnot shown), a transmission case 55 c, an electric motor case 55 d, and areduction gear case 55 e.

FIG. 2 is a sectional side view of the power unit according to thepresent invention.

As will be fully described with reference to FIG. 8, the power unit 15includes a four-cycle engine in which an intake cam shaft and an exhaustcam shaft are provided in a cylinder head. The power unit 15 has a crankshaft 56 disposed in a lower portion of the power unit case 55; a clutchshaft 57 disposed in parallel to and higher than the crank shaft 56; anda transmission shaft 58 and an electric motor shaft 59 disposed in sucha manner as to extend from one end of the clutch shaft 57 in thelongitudinal direction (fore and aft) of the vehicular body. That is tosay, the clutch shaft 57, transmission shaft 58, and electric motorshaft 59 are disposed in series and also in parallel to and higher thanthe crank shaft 56.

Since the clutch shaft 57, transmission shaft 58, and electric motorshaft 59 are disposed in series in the longitudinal direction of thevehicular body, the direction of a force applied to the power unit case55 becomes simple. This facilitates the design of the power unit case55. Concretely, the power unit case 55 can be designed such that therigidity is high in the direction where the force is applied and therigidity is low in the direction where the force is not applied; andconsequently, the power unit case 55 can be reduced in weight and alsobe made compact as a whole in proportional to simplification of theforce applied to the power unit case 55.

In FIG. 2, reference numeral 75 indicates an epicycle reduction gear; 76is a potentiometer for detecting a rotational angle of a transmissioncontrol motor 95 to be described later; 121 is a cam shaft drive pulley;78 is a water pump driven by the pulley 121; 79 is a belt cover; and 103a is an oil pump case disposed at a lower central portion of the figure.

A primary drive gear 61, a primary driven gear 62, a centrifugal clutch67, and a transmission 70, (which are further added with an electricmotor shaft 59 when the electric motor 80 is operated for assisting theengine power), constitutes a power transmission system for transmittingpower from the engine; and the electric motor shaft 59 when the electricmotor 80 is operated constitutes a power transmission system fortransmitting power from the electric motor.

The details of components associated with the clutch shaft 57,transmission shaft 58, and electric motor shaft 59 will be fullydescribed with reference to the following figure.

FIG. 3 is a sectional plan view of the power unit according to thepresent invention. The details of the components associated with theclutch shaft, transmission shaft, and electric motor shaft, and thedrive force transmission configuration will be described with referenceto this figure.

The primary driven gear 62 rotatably mounted on the clutch shaft 57 isdriven by the primary drive gear 61 mounted on the crank shaft 56. Theprimary driven gear 62 drives a clutch outer 64 of a one-way clutch 63for a starter and a clutch inner 68 of the centrifugal clutch 67independently from the clutch shaft 57. For this purpose, the primarydriven gear 62 is connectable to both the clutch outer 64 of the one-wayclutch 63 and the clutch inner 68 of the centrifugal clutch 67 by meansof a cylindrical member. As the centrifugal clutch inner 68 is rotatedat a rotational speed of a specific value or more, a centrifugal clutchouter 69 is rotated together with the centrifugal clutch inner 68, witha result that the clutch shaft 57 starts to be rotated

The above primary drive gear 61 includes a phase difference adjustingsub-gear 61 a and a spring 61 b for preventing occurrence of gearrattle.

The transmission 70, which is of a cone type with its function fullydescribed with reference to another figure, transmits a power in theorder of the transmission shaft 58 → an inner disk 71 → cone 72 → anouter cup 73. The rotation of the outer cup 73 is transmitted to theelectric motor shaft 59 through a one-way clutch 83.

The electric motor 80 is of a coreless type, in which a permanent magnettype rotor 81 is mounted on the electric motor shaft 59 and a statorcoil 82 is mounted on an electric motor case 55 d.

When the centrifugal clutch 67 is turned on, a drive force istransmitted in the order of the clutch shaft 57, transmission shaft 58,transmission 70, and electric motor shaft 59, and acts to drive an axle90 through a multi-disk type torque limiter 84 and a reduction gearmechanism 85 (which is composed of a small gear 86, a large gear 87, asmall gear 88, and a large gear 89).

The multi-disk type torque limiter 84 includes a limiter inner 84 arotated together with the electric motor shaft 59, disks 84 b and 84 c(the disk 84 b is mounted on the limiter inner 84 a and the disk 84 c ismounted on the following limiter outer 84 d), a limiter outer 84 d, anda spring 84 e. The small gear 86 is integrated with the limiter outer 84d.

Power is transmitted in the order of the limiter inner 84 → disk 84 b →disk 84 c → limiter outer 84 d → small gear 86. If an excess torque overa predetermined value is applied, there occurs a slip between the disks84 b and 84 c for protecting the components of the multi-disk torquelimiter 84. The predetermined torque can be set by the spring 84 e.

The one-way clutch outer 64 for a starter acts as a flywheel and has abalance weight 91 for taking an engine balance. The one-way clutch outer64 constitutes the one-way clutch 63 for transmitting rotation of astarter in combination with the one-way clutch inner 65.

When a starter driven gear 93 is rotated by a starter (not shown), thecentrifugal clutch inner 68 is rotated through the one-way cutch inner65 and the one-way clutch outer 64, to start operation of the engine.And, when the one-way clutch outer 64 is rotated at a higher speed, itis separated from the clutch inner 65 on the low speed side.

In FIG. 3, the cam shaft drive pulley 121 for driving a cam shaft or thelike is provided on the other end (from end) of the crank shaft 56. Abelt 122 is driven by the pulley 121. The details of the pulley 121 andthe belt 122 will be fully described later.

FIGS. 4 and 5 are views illustrating configuration and a function of thecone type continuously variable transmission according to the presentinvention.

In the state of the cone 72 shown in FIG. 4, a relationship of R1>R2 isgiven, where R1 is a distance from the center of a cone supporting shaft74 to the inner disk 71, that is, a rotational radius of the inner disk71, and R2 is a distance from the center of a core supporting shaft 74to the outer cup 73, that is, a rotational radius of the outer cup 73.

The cone 72 is rotated at a low speed because a large diameter portion(radius: R1) of the cone 72 is rotated by the inner disk 71, and theouter cup 73 is rotated at a low speed because the outer cup 73 isrotated by the small diameter portion (radius: R2) of the cone 72.

When rotation of the outer cup 73 is higher than that of the electricmotor shaft 59, power is transmitted from the outer cup 73 to theelectric motor shaft 59 through the one-way clutch 83.

Reference numeral 70 a indicates a cam ball for pushing the outer cup 73leftward along with rotation of the outer cup 73. Such a pushing actionallows contact pressure to be applied between the outer cup 73 and thecone 72. Reference numerals 70 b, 70 c and 70 d indicate oil seals. Theoil seals 70 b and 70 c form a closed space for accumulatingtransmission oil in the transmission 70, and the oil seal 70 d cuts offoil on the crank case 55 b side (on the left side of the figure).Accordingly, there is no fear that oil in the crank case is mixed withtransmission oil.

In the state of the cone 72 shown in FIG. 5, a relationship of R3<R4 isgiven, where R3 is a distance from the center of the cone supportingshaft 74 to the inner disk 71, that is, a rotational radius of the innerdisk 71, and R4 is a distance from the cone supporting shaft 74 to theouter cup 73, that is, a rotational radius of the outer cup 73.

The cone 72 is rotated at a high speed because the small diameterportion (radius: R3) of the cone 72 is rotated by the inner disk 71, andthe outer cup 73 is rotated at a high speed because the outer cup 73 isrotated by the large diameter portion (radius: R4) of the cone 72.

By moving the cone 72 as shown in FIGS. 4 and 5, the transmission 70transmits rotation at a reduced speed, a uniform speed, or an increasedspeed.

For this purpose, as shown in FIG. 4, a control gear 97 is shifted bythe transmission control motor 95 through gears 96 a, 96 b and 96 c. Thecontrol gear 97 has a trapezoid female thread portion 99 formed on itsboss portion. The trapezoid female thread portion 99 is meshed with atrapezoid male thread portion 98 fixed on the case 55 side. The controlgear 97 is shifted leftward in the figure by spiral motion of thetrapezoid female thread portion 99. The leftward shift of the controlgear 97 moves the cone 72 leftward in the figure together with the conesupporting shaft 74 into the state shown in FIG. 5.

It is important that both the trapezoid male thread portion 98 and thetrapezoid female thread portion 99 are provided not on the outer cup 73side but on the inner disk 71 side. The cone 72 is pushed leftward inthe figure by reaction of the outer cup 73. As a result, the controlgear 97 is applied with a force in the direction shown by an arrow “1”,that is , in the direction from the low speed side to the high speedside. With the configuration in this embodiment, the cone 72 can beshifted to the high speed side with a small torque. This is effective tolower the capacity of the transmission control motor 95.

A lubricating system will be described below.

FIG. 6 is a view illustrating an engine lubricating system according tothe present invention, in which flow of oil is indicated by an arrow.

The power unit case 55 has a lower oil tank 101 disposed at its lowerportion, and an upper oil tank 102 disposed at its upper portion. Afirst oil pump 103, a second oil pump 104, and a third oil pump 105 arecoaxially disposed on one end side (right end side) of the crank shaft56. First, oil in the lower oil tank 101 is pumped by the first oil pump103 through a strainer 106 and a first oil passage 107, and is suppliedto the upper oil tank 102 through a second oil passage 108.

The oil in the upper oil tank 102 flows to the second oil pump 104through a third oil passage 109 and is pressurized by the second oilpump 104. The oil thus pressurized lubricates main journal portion 56 a,a connecting rod large end portion 56 b, and others (particularly, avalve chamber not shown) through a fourth oil passage 111, a filter 112,and a fifth oil passage 113, and returns to the lower oil tank 101. Inthis figure, reference numeral 112 a indicates a filter cover.

FIG. 7 is a view illustrating a transmission lubricating systemaccording to the present invention. Referring to FIG. 7, transmissionoil is pumped from a transmission oil tank 115 additionally provided ona lower portion of the power unit case 55 by the third oil pump 105through a six oil passage 116, being fed to the transmission shaft 58through a seventh oil passage 117, and is supplied to the transmission70 through an oil passage 118 in the transmission shaft 58. The oil isthen returned to the transmission oil tank 115 in the direction shown byan arrow in the figure, and is pumped by the third oil pump 105 througha strainer 119.

FIG. 8 is a front view of the power unit, showing a cam shaft drivemechanism as a valve drive mechanism according to the present invention.

Referring to FIG. 8, the left crank case 55 a is mounted on the rightside of a cylinder block 129B integrated with the right crank case 55 b,and the electric motor 80 is disposed higher than the crank shaft 56. Acylinder head 129H is mounted on the left side of the cylinder block129B. The muffler 21 is mounted at the leading end of the exhaust pipe19 extending from the cylinder head 129H. An intake manifold 129Mextending from the air cleaner 18 on the upper left side (and on theback side of the figure) is connected to the cylinder head 129H througha carburetor 129C. Reference numeral 129S indicates a starter motormounting hole.

In FIG. 8, since a belt cover 79 is removed, there can be seen, from thefront side of the power unit 15, a cam shaft drive mechanism 120 as thevalve drive mechanism composed of a cam shaft drive pulley 121, a belt122, an intake side cam shaft pulley 123, an exhaust side cam shaftpulley 124, and a tensioner 125.

As is apparent from FIG. 8, since the cylinder is disposed in the widthdirection of the vehicular body with its cylinder axis 126 substantiallyin the horizontal direction (for example, a tilt angle with respect tothe ground is set at +10°), the center of gravity of the vehicle islowered and also the cylinder length can be set within the vehicularwidth. This increases the degree of design of the vehicle.

In FIG. 8, which is seen in the direction from the front wheel side tothe rear wheel side, both the crank shaft 56 and the clutch shaft 57 aredisposed on the right side from a body center 127, and the cylinder head129H is disposed on the left side from the body center 127. Behind theclutch shaft 57 in the figure are disposed the shafts of “the powertransmission system” such as the transmission shaft 58 and the electricmotor shaft 59, as described with reference to FIGS. 2 and 3.

Referring to FIG. 8, the cylinder head 129H including two cam shafts(not shown) and the like is sufficiently heavy and acts as a counterweight which is balanced with the power unit case 55, disposed on theright side of the figure, including the crank shaft 56, clutch shaft 57,and the like. Accordingly, it is possible to easily solve the lateralimbalance.

The power unit 15 in this embodiment includes the electric motor 80 inaddition to the engines and since the crank shaft 56 and the electricmotor shaft 59 are disposed in the longitudinal direction (fore and aft)of the vehicular body, it is possible to facilitate the layout of theequipment.

The present invention may be also applied to a motorcycle using agasoline engine as a drive source.

INDUSTRIAL APPLICABILITY

The present invention having the above arrangement achieves thefollowing advantages:

In one aspect of the present invention, since the crank shaft and thepower transmission system are disposed on one side and the cylinder headis disposed on the other side, it is possible to improve the weightbalance of the power unit, and hence to ensure a favorable steeringstability of the motorcycle.

In another aspect of the present invention, since the crank shaft andthe power transmission system are disposed on one side and the cylinderhead including a valve drive mechanism is disposed on the other side, itis possible to improve the weight balance of the power unit, and henceto ensure a favorable steering stability of the motorcycle.

In a further aspect of the present invention, since the powertransmission system including the electric motor and the crank shaftdisposed on one side and the cylinder head is disposed on the otherside, it is possible to improve the weight balance of the power unit,and hence to ensure a favorable steering stability of the motorcycle.

In a still further aspect of the present invention, since the crankshaft and the power transmission system are disposed on one side, andthe cylinder head and members of the intake and exhaust system aredisposed on the other side, it is possible to improve the weight balanceof the power unit, and hence to ensure a favorable steering stability ofthe motorcycle.

What is claimed is:
 1. A power unit arrangement structure for amotorcycle, said motorcycle having a body and a main frame, said powerunit arrangement structure comprising a power unit including an engine,an electric motor, and a power transmission system, said powertransmission system for transmitting power of said engine and fortransmitting power of this electric motor and being disposable on oneside of a rear wheel of the motorcycle, said engine being disposed witha crank shaft extending longitudinally of said body, said power unitarrangment structure further including means for mounting said powerunit to said main frame of said motorcycle so that said crank shaft andsaid power transmission system are disposable on one side with respectto a longitudinal center of said motorcycle body and a cylinder head ofthe engine extends on the other side with respect to the longitudinalcenter, said power transmission shaft being disposed parallel to andhigher than said crank shaft.
 2. A power unit arrangement structure fora motorcycle according to claim 1, wherein said cylinder head is acylinder head of a four cycle engine.
 3. A power unit arrangementstructure for a motorcycle according to claim 1 or 2, wherein saidmounting means supports members of an intake, system and members of anexhaust system disposed on said cylinder head side.